There have been many different types and kinds of proximity detectors. They have usually employed electrical switches which are actuated when a conductor, such as a body of water, moves into close proximity to a sensor.
For example, the following are U.S. patents disclosing several such detectors and systems: U.S. Pat. Nos. 3,588,859; 3,665,300; 4,800,755; 4,875,497 and U.S. Pat. No. 5,017,909. For example, in the U.S. Pat. No. 5,017,909, there is disclosed a proximity detector used as a liquid level detector. Such a detector is used to detect liquid level receptacles employed with vehicles.
Other applications for liquid level detectors include pumping systems, such as a bilge pumping system for ships. Such a pumping system must be activated before the accumulated water reaches an unsafe level. In this regard, detection of an unsafe water level is usually accomplished by mechanical floatation systems, which cause a switch to be actuated whenever the water reaches such an undesired level.
Prior known liquid level detection systems have generally proven to be less than satisfactory for some applications, because they have included a number of parts which are subject to mechanical failure, as well as corrosion due to exposure to moisture.
Therefore, it would be highly desirable to have a new and improved proximity detection system which is highly reliable and relatively inexpensive to manufacture. Such a proximity detection system should be highly sensitive and possess a wide range of applications.